Therefore we also investigated the variability in nitrogen isotopecomposition within the individual organisms in our study. Limpetsfrom two locations (7 and 14) were dissected, and different tissuesof the body (muscle, digestive organs, head, mantle) were analysedseparately. The variations in nitrogen isotope composition of thetissues are presented in Fig. 4. The results of the mean ı15N val-ues show fractionation in the following way: head (7.05‰), muscle(6.74‰), digestive organs (6.72‰) and mantle (6.41‰). Differencesin mean ı15N values between tissues within a single organism werebelow 0.7‰.